Hi Julian, Thank you for your fast answer! A 1st point, as with the FT857, i'm using USB mode for JT65A. For the filter used, i ordered a 8 poles 2.8k with my K3, but i'm not sure if the 5 poles 2.7k "original" and always installed as FIL2 is not selected during TX???; next week-end, when active at my "external" shack, i will look how to remove the 2.7k filter, as i've also problem with center filter when i adjust the HI LO filter controls; when the 2.7k filter is (automatically) selected, i've a big discontinuity with filter setting.
As you say, i will look if the 2.7k is not selected during TX. I read also the "problems" when in DATA A mode, but as said, i'm working in USB (as recommended for JT65A for all RF bands) and VOX work at perfection too. My best 73, Rudolf HB9ARI PS As i expect to get 50W output when i set the control to 50W, i've adjusted the audio input level for max bars on ALC. For PSK31, i work with ~ 10 to15W max for 100W selectes with the control and "local" receiving give me an "acceptable" -24 to -28dB IMD. Julian, G4ILO wrote: > hb9ari wrote: > >> Hello, >> >> As i use principally JT65A (snice ~ 2years), >> i've remarked transmit output power variations >> depending where the audio is located in the waterfall, >> as i'm not speaking English, it's difficult to explain correctly; >> if i'm ~ in the middle of the waterfall (~ 1200Hz) >> i get over 3dB in output power variations; for an expected >> 50W output power, between some tones of the JT65A >> modulation, the output level can vary from 20W >> to 60W; if i'm working away from the "middle", >> variations are lower and acceptable but most >> of time, "central" frequencies are used... >> I've always worked with this "problem" as i >> expect some AGC effect by the receiving side... >> I would appreciate to have an explanation >> of this effect. >> >> >> > > This topic has been brought up before in the context of RTTY. The reason is > that there is no automatic level control in DATA A mode (or rather, there > is, but it is very slow acting to avoid causing IMD on PSK31 signals) so > there is no compensation for ripples in the roofing filter passband. It has > been suggested that the problem is less when using the 8-pole SSB roofing > filter as it has less ripple than the standard 5-pole filter. > > The output should not vary as much as you suggest while working within the > normal passband for JT65A operation so I'm wondering if you have correctly > adjusted the audio input level in DATA A to get 5 bars on the ALC scale. > This will not prevent the power varying for different tones during a > transmission but it should help maintain a constant average level when > working at different places within the passband. > > ----- > Julian, G4ILO. K2 #392 K3 #222. > * G4ILO's Shack - http://www.g4ilo.com > * KComm - http://www.g4ilo.com/kcomm.html > * KTune - http://www.g4ilo.com/ktune.html > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
